EP2053018A1 - "Borohydride foam; production method; hydrogen generation method using borohydride foam. - Google Patents
"Borohydride foam; production method; hydrogen generation method using borohydride foam. Download PDFInfo
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- EP2053018A1 EP2053018A1 EP08167150A EP08167150A EP2053018A1 EP 2053018 A1 EP2053018 A1 EP 2053018A1 EP 08167150 A EP08167150 A EP 08167150A EP 08167150 A EP08167150 A EP 08167150A EP 2053018 A1 EP2053018 A1 EP 2053018A1
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- Prior art keywords
- foam
- borohydride
- catalytic material
- alkaline earth
- solvent
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
- C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
- C01B3/06—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of inorganic compounds containing electro-positively bound hydrogen, e.g. water, acids, bases, ammonia, with inorganic reducing agents
- C01B3/065—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of inorganic compounds containing electro-positively bound hydrogen, e.g. water, acids, bases, ammonia, with inorganic reducing agents from a hydride
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B6/00—Hydrides of metals including fully or partially hydrided metals, alloys or intermetallic compounds ; Compounds containing at least one metal-hydrogen bond, e.g. (GeH3)2S, SiH GeH; Monoborane or diborane; Addition complexes thereof
- C01B6/06—Hydrides of aluminium, gallium, indium, thallium, germanium, tin, lead, arsenic, antimony, bismuth or polonium; Monoborane; Diborane; Addition complexes thereof
- C01B6/10—Monoborane; Diborane; Addition complexes thereof
- C01B6/13—Addition complexes of monoborane or diborane, e.g. with phosphine, arsine or hydrazine
- C01B6/15—Metal borohydrides; Addition complexes thereof
- C01B6/19—Preparation from other compounds of boron
- C01B6/21—Preparation of borohydrides of alkali metals, alkaline earth metals, magnesium or beryllium; Addition complexes thereof, e.g. LiBH4.2N2H4, NaB2H7
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis
Definitions
- This new material finds particular application as a fuel for fuel cells. More particularly, in the context of this application, the present invention relates to fuel cells for the power supply of portable electrical or electronic devices, that is to say devices requiring low electrical power. The present invention may, however, also find application for supplying hydrogen fuel cells of higher powers.
- One of the known hydrogen production methods consists of hydrolyzing borohydrides, in solid or liquid form, such as borohydride or sodium tetrahydroborate NaBH 4 , dissolved and brought into contact with a solid state catalytic material.
- the hydrolysis reaction of such a borohydride takes place under certain conditions according to the following reaction scheme: M (BH 4 ) n + 2nH 2 O ---> M [B (OH) 4 ] n + 4nH 2
- M is an alkaline or alkaline earth element and n is a positive integer equal to the number of valence electrons of the element M.
- This element M may therefore, for example, be sodium (Na), in which case the number n is equal to 1, which leads to the following reaction scheme: NaBH 4 + 2H 2 O ---> NaB (OH) 4 + 4H 2 .
- the element M may also consist of potassium (K), lithium (Li) or another suitable element.
- sodium borohydride commonly used, generates four moles of hydrogen by reacting with two moles of water.
- an aqueous solution of sodium borohydride is used and, to facilitate the reaction, catalysts.
- This aqueous solution is brought into contact with a catalytic material; typically, it passes on a catalytic bed, in order to generate hydrogen.
- Flow control of the borohydride solution controls the reaction.
- the yield being defined here as the ratio of the mass of hydrogen generated to the fuel mass used.
- the use of a borohydride solution has a major disadvantage for the application to fuel cells, in particular for portable devices: the solubility in water of sodium borohydride and its reaction product is relatively weak.
- the borohydride solutions are not stable over time: they hydrolyze by generating hydrogen (H 2 ), which proves troublesome for storage.
- the patent US6,746,496 thus describes micro-dispersed powders of borohydride particles containing a reaction catalyst.
- the patent application FR 2,892,111 it describes a borohydride powder whose grains are covered in whole or in part by particles of catalytic material. Said coated grains are obtained from, on the one hand, a suspension of powder grains ("virgin") and, on the other hand, of a solution containing in solution a salt or alloy or oxide of at least one metal noble or not noble.
- Said powder grains "virgin” have a specific surface between 0.5 and 100 m 2 .g -1 , preferably between 1 and 10 m 2 .g -1 .
- the patent application WO 2005/005311 deals with obtaining tablets or pellets by compression of catalyzed borohydride powders (intimate mixtures obtained by evaporation of a solvent).
- the same patent application WO 2005/005311 also presents materials obtained by deposition of borohydride (optionally catalyzed) on supports (porous material type or metal or organic foam).
- the Applicant is currently proposing a new material capable of generating hydrogen by hydrolysis of at least one borohydride, making it possible to better control the kinetics of reaction, therefore the flow of hydrogen generated, and further to limit the formation of a passivating layer.
- the invention relates to a material consisting of a foam of at least one borohydride of alkali metal or alkaline earth metal; said foam having a specific surface area of between 1.5 m 2 .g -1 and 10 m 2 .g -1 .
- the element (s) constituting (s) said material is (are) not per se original (aux): at least one borohydride of an alkali metal or alkaline earth metal, usually a borohydride of a alkali metal or borohydride of an alkaline earth metal; mixtures of at least two alkaline borohydrides, at least two alkaline earth borohydrides, or even at least one alkaline borohydride and at least one alkaline earth borohydride (mixed mixtures) are however not excluded.
- What is original is the shape of the material.
- the said constituent element (s) has been conditioned into a solid foam having a specific surface as indicated above.
- the material of the invention is new in that it is a solid foam having such a specific surface.
- This concept of solid foam is familiar to those skilled in the art, in contexts different from that of the invention.
- the expression "solid foam” in said contexts, and therefore in the present description and the appended claims, means a homogeneous solid material with a high porosity and a specific surface area.
- the specific surface area of said foam is greater than 1.0 m 2 .g -1 (it is a foam): it is between 1.5 m 2 .g -1 and 10 m 2 .g -1 . It is an open porosity, free, although it is not excluded that some pores are closed.
- the specific surface area values set forth above for the foams of the invention are sufficiently high to characterize foams but are, in any case, not very high (for foams).
- the foams of the invention contain sufficient large pores (in view of said specific surface values) for allow easy penetration of the hydrolysis reagent within said foams (the hydrolysis reaction is developed in the volume of said foams), to optimize the borohydride reaction (s) / hydrolysis reagent within said foams.
- the foams of the invention actually offer an optimum in terms of reactive surface (overall) and accessibility to said reactive surface.
- alkali or alkaline earth metal is involved and it is chosen from the group comprising sodium (Na), lithium (Li) and magnesium (Mg). ).
- NaBH 4 sodium tetrahydroborate is the most advantageous because it is easy to produce and inexpensive.
- the basic borohydride powders (raw materials useful for obtaining the foams of the invention: see the production process described below) generally have a specific surface area of between 0.05 and 0.1 m 2 / g. (The skilled person is aware that such low values depend on the gas absorbed for the implementation of the measure).
- the foams of the present invention have a surface area more than 10 times greater than that of said basic borohydride powders (the measurement of specific surfaces of this order is much less dependent on the nature of the gas absorbed).
- borohydride powders which can be used to obtain foams of the invention, have a higher specific surface, and in particular a specific surface area of the order of that indicated for the foams of the invention.
- the coincidence of specific surface values (foams / powders) is only fortuitous.
- the borohydride foam (s) of the invention may contain, in intimate mixture with (embedded in) the said borohydride (s) (within its constitutive element (s) ), catalytic material (particles of catalytic material) capable (s) to catalyze the reaction of hydrogen generation by hydrolysis of (or said) borohydride (s).
- catalytic material particles of catalytic material capable (s) to catalyze the reaction of hydrogen generation by hydrolysis of (or said) borohydride (s).
- This catalytic material obviously intervenes with reference to the main outlet of the foams of the invention, presented in the introduction of this text.
- the foams of the invention, catalysed or not may have other outlets. They can be used in other contexts.
- the particle size of said catalytic material is as small as possible.
- the particles of catalytic material therefore generally consist of nanoparticles which have a median diameter of between 1 and 100 nm, advantageously between 3 and 5 nm.
- Such nanoparticles make it possible to obtain an intimate mixture with the metal borohydride.
- Their obtaining process is for example described in the following reference: Small C.; Pileni MP "Nanosize cobalt boride particles: control of the size and properties", Journal of Magnetism and Magnetic Materials vol. 166, p. 82-90, 1997 .
- the catalysed foams of the invention generally contain from 0.5% to 30% by weight of catalytic material, advantageously at most 10%, very advantageously between 1 and 10%.
- Said catalytic material in intimate mixture with said borohydride (s), may consist of at least one metal selected from the group comprising platinum (Pt), ruthenium (Ru), palladium (Pd) ), cobalt (Co), nickel (Ni), iron (Fe), gold (Au), silver (Ag), manganese (Mn), rhenium (Re), rhodium (Rh) ), titanium (Ti), vanadium (V) and cerium (Ce), or by at least one alloy, or salt or oxide of at least one of said metals.
- platinum Pt
- Ru ruthenium
- Ru palladium
- Co cobalt
- Ni nickel
- Fe iron
- Au gold
- silver Ag
- Mn manganese
- Re rhenium
- Rhodium titanium
- Ti titanium
- V vanadium
- Ce cerium
- the salt in question is a chloride, a boride or an organometallic salt of at least one of the above metals, and for example cobalt boride or nickel boride, both of which are good catalysts.
- the foams of the invention make it possible to generate hydrogen, by implementing a heterogeneous, solid-liquid, easily controllable reaction, whatever its degree of advancement.
- the invention relates to a method for producing such foams.
- the properties (porosity, specific surface area) of the solid foam obtained depend on the conditions of implementation of the process for obtaining said foam and more particularly on the conditions for carrying out stirring, bubbling and blowing. Evaporation of the solvent. The management of these conditions, their optimization, in view of the desired result (specific surface values) falls within the knowledge of those skilled in the art.
- the "block” of foam obtained can obviously be crushed to generate pieces (smaller) of foam.
- the optional intermediate step specified above is carried out.
- the bubbling is carried out in a solution, in the absence of catalytic material, in a suspension, in the presence of catalytic material.
- solvent suitable for carrying out the above process, that is to say a solvent for the metal borohydride (s) retained.
- solvent solvent in which the catalytic material which intervenes possibly is insoluble.
- the method of the invention has the advantage of being independent of the particle size of the borohydride (raw material), said borohydride being dissolved in the solution.
- the particle size of the catalytic material has a certain importance and in the context of the process of the invention it can be optimized without difficulty. It is indeed perfectly controllable insofar as said catalytic material intervenes in the solid state (in the form of particles) and remains in suspension (in the same solid state, in the form of particles).
- the particles of catalytic material generally have a median diameter of between 1 and 100 nm, advantageously between 3 and 5 nm. Such nanoparticles make it possible to obtain an intimate mixture with the metal borohydride.
- the present invention also relates to a process for generating hydrogen by hydrolysis of at least one foam of the invention (foam as described above and / or as produced by the method described above). Said method is advantageously used for the supply (in hydrogen) of a fuel cell. When the foam contains catalytic material, activation of the hydrolysis reaction requires no catalyst transport by the hydrolyzing phase.
- FIGS. 1A, 1B, 1C show the appearance, observed under a scanning electron microscope (at different magnifications), of a basic sodium borohydride powder serving as an ingredient (of raw material) for carrying out the process of the invention.
- FIGS. 2A, 2B, 2C show a foam, object of the invention, observed under a scanning electron microscope, at different magnifications.
- the sodium borohydride, of formula NaBH 4 is said to be dry because it is previously dehydrated at 150 ° C. under primary vacuum during 2 hours.
- the particle size or specific surface of the borohydride does not matter since said borohydride to be dissolved.
- the FIGS. 1A, 1B and 1C show images of scanning electron microscopy, at different magnifications, grains typical of basic sodium borohydride used as an ingredient. It is dense grains of about 50 to 200 microns, having a smooth surface.
- the sodium borohydride powder (NaBH 4 ) used in the example described has a specific surface area of 0.08 m 2 .g -1 .
- the exemplified process also comprises the production of the particles of catalytic material, by reduction of a salt or an alloy or an oxide of at least one metal, according to methods described in the literature.
- the particle size of the particles of catalytic material is important in the context of the process of the invention, since these particles remain in suspension in the solvent (in the following process) until evaporation of said solvent.
- the smallest possible particle sizes are advantageously chosen, i.e. particles having a median diameter preferably less than 100 nm, very preferably less than 10 nm (see above).
- an argon bubbling (flow rate of 20 l / min) is implemented by means of a capillary tube plunger in the solution and the temperature is gently brought down to ambient (1 ° C / 3min), which causes the evaporation of ammonia. Stirring is maintained throughout the duration (about 20 minutes) of evaporation of ammonia.
- bubbling argon and stirring are stopped.
- the medium is then put under reduced pressure to a pressure of 10 -2 mbar and heated for 8 hours at 60 ° C. until a gray solid corresponding to the formed borohydride foam containing the catalytic material (foam which is an example of a foam according to the present invention). This foam must be stored away from moisture.
- the obtained material is in the form of an open-pore foam, as shown by the three images obtained by scanning electron microscopy, for different magnifications, shown on the FIGS. 2A, 2B and 2C ;
- the specific surface area (determined by the BET method, a method for determining the specific surface area based on the adsorption of gas, nitrogen or krypton, for example, at low temperature, in a monolayer on the surface of the sample to be analyzed) of the said foam being 1.61 m 2 .g -1 (and its density is 1.2 g.cm -3 ).
- the material according to the present invention makes it possible to limit the formation of a passivating layer, that is to say a layer consisting of the by-products of the hydrolysis reaction. Indeed, the metaborates formed by contact between water, the catalyst and sodium tetrahydroborate are distributed on the surface of the foam, and thus, do not constitute a continuous and blocking layer.
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Abstract
Description
La présente invention a pour objet :
- un nouveau matériau : une mousse solide d'au moins un borohydrure de métal alcalin ou alcalino-terreux ; ladite mousse pouvant aussi renfermer une matière catalytique ;
- un procédé de production de ce matériau ;
- l'utilisation de ce matériau pour générer de l'hydrogène par hydrolyse ; en d'autres termes, un procédé de génération d'hydrogène par hydrolyse dudit matériau.
- a new material: a solid foam of at least one alkali or alkaline earth metal borohydride; said foam may also contain a catalytic material;
- a method of producing this material;
- the use of this material to generate hydrogen by hydrolysis; in other words, a process for generating hydrogen by hydrolyzing said material.
Ce nouveau matériau trouve notamment application en tant que combustible pour les piles à combustible. Plus particulièrement, dans le cadre de cette application, la présente invention concerne les piles à combustible destinées à l'alimentation électrique d'appareils électriques ou électroniques portables, c'est-à-dire d'appareils nécessitant une puissance électrique faible. Ladite présente invention peut cependant trouver également application pour alimenter en hydrogène des piles à combustible de puissances supérieures.This new material finds particular application as a fuel for fuel cells. More particularly, in the context of this application, the present invention relates to fuel cells for the power supply of portable electrical or electronic devices, that is to say devices requiring low electrical power. The present invention may, however, also find application for supplying hydrogen fuel cells of higher powers.
L'un des modes de production d'hydrogène connu consiste à hydrolyser des borohydrures, sous forme solide ou liquide, comme le borohydrure ou tétrahydroborate de sodium NaBH4, mis en solution et mis en contact avec une matière catalytique à l'état solide. La réaction d'hydrolyse d'un tel borohydrure s'opère sous certaines conditions selon le schéma réactionnel suivant :
M(BH4)n + 2nH2O ---> M[B(OH)4]n + 4nH2
où M est un élément alcalin ou alcalinoterreux et n est un nombre entier positif égal au nombre d'électrons de valence de l'élément M. Cet élément M peut donc, par exemple, être du sodium (Na), auquel cas le nombre n est égal à 1, ce qui conduit au schéma réactionnel suivant :
NaBH4 + 2H2O ---> NaB(OH)4 + 4H2.
One of the known hydrogen production methods consists of hydrolyzing borohydrides, in solid or liquid form, such as borohydride or sodium tetrahydroborate NaBH 4 , dissolved and brought into contact with a solid state catalytic material. The hydrolysis reaction of such a borohydride takes place under certain conditions according to the following reaction scheme:
M (BH 4 ) n + 2nH 2 O ---> M [B (OH) 4 ] n + 4nH 2
where M is an alkaline or alkaline earth element and n is a positive integer equal to the number of valence electrons of the element M. This element M may therefore, for example, be sodium (Na), in which case the number n is equal to 1, which leads to the following reaction scheme:
NaBH 4 + 2H 2 O ---> NaB (OH) 4 + 4H 2 .
L'élément M peut aussi être constitué par du potassium (K), du lithium (Li) ou un autre élément approprié.The element M may also consist of potassium (K), lithium (Li) or another suitable element.
Selon ce schéma réactionnel, le borohydrure de sodium, couramment utilisé, génère quatre moles d'hydrogène en réagissant avec deux moles d'eau.According to this reaction scheme, sodium borohydride, commonly used, generates four moles of hydrogen by reacting with two moles of water.
En général, on utilise une solution aqueuse de borohydrure de sodium et, pour faciliter la réaction, des catalyseurs. Cette solution aqueuse est mise en contact avec une matière catalytique ; typiquement, elle passe sur un lit catalytique, afin de générer l'hydrogène. Le contrôle du débit de la solution de borohydrure permet de contrôler la réaction. Néanmoins, on a constaté qu'un tel mode de génération d'hydrogène présente un rendement assez faible ; le rendement étant ici défini comme le rapport de la masse d'hydrogène générée à la masse de combustible mise en oeuvre. En effet, l'utilisation d'une solution de borohydrure présente un inconvénient majeur pour l'application aux piles à combustible, en particulier celle destinées aux appareils portables : la solubilité dans l'eau du borohydrure de sodium et de son produit de réaction est relativement faible.In general, an aqueous solution of sodium borohydride is used and, to facilitate the reaction, catalysts. This aqueous solution is brought into contact with a catalytic material; typically, it passes on a catalytic bed, in order to generate hydrogen. Flow control of the borohydride solution controls the reaction. Nevertheless, it has been found that such a mode of hydrogen generation has a rather low yield; the yield being defined here as the ratio of the mass of hydrogen generated to the fuel mass used. Indeed, the use of a borohydride solution has a major disadvantage for the application to fuel cells, in particular for portable devices: the solubility in water of sodium borohydride and its reaction product is relatively weak.
Ainsi, il faut environ 3,8 moles d'eau pour solubiliser une mole de borohydrure de sodium (NaBH4) et 13,3 moles d'eau pour solubiliser une mole du produit de réaction (NaBO2). La quantité d'eau à utiliser pour obtenir, soit une solution de borohydrure de sodium, soit une solution dans laquelle le produit de réaction est soluble, est donc bien supérieure à la quantité d'eau nécessaire à la simple réaction d'hydrolyse.Thus, about 3.8 moles of water are required to solubilize one mole of sodium borohydride (NaBH 4 ) and 13.3 moles of water to solubilize one mole of the reaction product (NaBO 2 ). The amount of water to be used to obtain either a solution of sodium borohydride or a solution in which the reaction product is soluble is therefore much greater than the amount of water required for the simple hydrolysis reaction.
Par conséquent, le rendement réel de génération d'hydrogène est plus faible que le rendement théorique (10,8%). Il serait ainsi d'environ 7% si la solution solubilisait uniquement le borohydrure de sodium (NaBH4), mais il est de l'ordre de 3% seulement car la solution solubilise ledit borohydrure de sodium (NaBH4) et le produit de réaction (NaBO2). Il n'existe donc pas à l'heure actuelle de générateur d'hydrogène à base de solution de borohydrure de sodium, capable de travailler avec des rendements supérieurs à 4%.As a result, the actual hydrogen generation efficiency is lower than the theoretical yield (10.8%). It would thus be about 7% if the solution solubilized only sodium borohydride (NaBH 4 ), but it is of the order of 3% only because the solution solubilizes said sodium borohydride (NaBH 4 ) and the reaction product. (NaBO 2 ). There is therefore currently no hydrogen generator based sodium borohydride solution, capable of working with yields greater than 4%.
En outre, il convient de remarquer que, de façon générale, les solutions de borohydrure ne sont pas stables dans le temps : elles s'hydrolysent en générant de l'hydrogène (H2), ce qui s'avère gênant pour le stockage.In addition, it should be noted that, in general, the borohydride solutions are not stable over time: they hydrolyze by generating hydrogen (H 2 ), which proves troublesome for storage.
Afin de se rapprocher du rendement théorique et d'élever la densité d'énergie du combustible, il est donc préférable d'utiliser uniquement la quantité d'eau stoechiométrique nécessaire à la réaction de génération d'hydrogène. Pour cela, il a été envisagé de mettre en oeuvre des borohydrures sous forme solide, en particulier à l'état divisé, c'est-à-dire sous forme pulvérulente. L'hydrogène est alors généré par addition de borohydrure solide à une solution aqueuse, contenant de préférence une matière catalytique.In order to approximate the theoretical yield and to increase the energy density of the fuel, it is therefore preferable to use only the amount of stoichiometric water required for the hydrogen generation reaction. For this, it has been envisaged to use borohydrides in solid form, in particular in the divided state, that is to say in powder form. The hydrogen is then generated by addition of solid borohydride to an aqueous solution, preferably containing a catalytic material.
Cependant, il est difficile de contrôler une telle réaction et, partant, le débit d'hydrogène généré. En effet, ce type de réaction hétérogène, c'est-à-dire mettant en jeu des réactifs à l'état liquide et à l'état solide, est difficile à contrôler, car il implique des mécanismes de diffusion, en l'occurrence la diffusion de l'eau vers le borohydrure. Or de tels mécanismes de diffusion dépendent fortement de la porosité du milieu réactif, qui elle-même, varie au cours de l'avancement de la réaction, du fait de la formation de sous-produits plus ou moins compacts.However, it is difficult to control such a reaction and hence the hydrogen flow rate generated. Indeed, this type of heterogeneous reaction, that is to say involving reagents in the liquid state and in the solid state, is difficult to control because it involves diffusion mechanisms, in this case the diffusion of the water towards the borohydride. However, such diffusion mechanisms strongly depend on the porosity of the reactive medium, which itself varies during the progress of the reaction, due to the formation of more or less compact by-products.
Des travaux ont été effectués pour tenter d'améliorer la diffusion de l'eau dans les substrats de borohydrure catalysés. Des matériaux découlant de ces travaux permettent de mieux contrôler la cinétique de réaction, donc le débit d'hydrogène généré, et en outre de limiter la formation d'une couche passivante. Il s'agit de borohydrures se présentant sous forme de poudres dont les grains sont recouverts, en tout ou partie, de matière catalytique, ou contiennent, ou sont intimement mélangés avec, des particules de matière catalytique.Work has been done to try to improve the diffusion of water in catalyzed borohydride substrates. Materials resulting from this work make it possible to better control the kinetics of reaction, and therefore the flow rate of hydrogen generated, and in addition to limit the formation of a passivating layer. These are borohydrides in the form of powders whose grains are covered, in whole or in part, with catalytic material, or contain, or are intimately mixed with, particles of catalytic material.
Le brevet
Même s'il est reconnu que les matériaux ci-dessus conduisent à une cinétique d'hydrolyse mieux maîtrisée, cette dernière reste encore insuffisante, notamment en raison de la formation d'une couche passivante limitant la diffusion de l'eau dans le substrat.Although it is recognized that the above materials lead to a better controlled kinetics of hydrolysis, the latter is still insufficient, in particular because of the formation of a passivating layer limiting the diffusion of water in the substrate.
La demande de brevet
- que leur porosité doit être suffisante pour recevoir un volume important d'hydrogène (ces matériaux sont en effet utilisés pour stocker l'hydrogène généré) ou pour permettre à l'hydrogène de passer à leur travers. L'homme du métier comprend qu'ils doivent donc présenter une surface spécifique importante (i.e. de "petits" pores) ;
- qu'ils peuvent être obtenus soit par action d'un gaz, avec variation de pression, soit par action d'un agent porogène susceptible de subir une réaction de décomposition chimique, thermique ou photolytique.
- that their porosity must be sufficient to receive a large volume of hydrogen (these materials are indeed used to store the hydrogen generated) or to allow hydrogen to pass through them. The skilled person understands that they must therefore have a high specific surface (i e "small"pores..);
- that they can be obtained either by the action of a gas, with variation of pressure, or by action of a porogenic agent capable of undergoing a chemical, thermal or photolytic decomposition reaction.
L'homme du métier est en fait toujours à la recherche d'un matériau solide, tel qu'un borohydrure, avantageusement catalysé, susceptible de conduire à une cinétique accélérée de génération d'hydrogène par hydrolyse.Those skilled in the art are in fact always looking for a solid material, such as a borohydride, advantageously catalyzed, likely to lead to accelerated kinetics of hydrogen generation by hydrolysis.
Dans un tel contexte, la Demanderesse propose présentement un nouveau matériau, apte à générer de l'hydrogène par hydrolyse d'au moins un borohydrure, permettant de mieux contrôler la cinétique de réaction, donc le débit d'hydrogène généré, et en outre de limiter la formation d'une couche passivante.In such a context, the Applicant is currently proposing a new material capable of generating hydrogen by hydrolysis of at least one borohydride, making it possible to better control the kinetics of reaction, therefore the flow of hydrogen generated, and further to limit the formation of a passivating layer.
Selon son premier objet, l'invention concerne un matériau consistant en une mousse d'au moins un borohydrure de métal alcalin ou alcalino-terreux ; ladite mousse présentant une surface spécifique comprise entre 1,5 m2.g-1 et 10 m2.g-1.According to its first object, the invention relates to a material consisting of a foam of at least one borohydride of alkali metal or alkaline earth metal; said foam having a specific surface area of between 1.5 m 2 .g -1 and 10 m 2 .g -1 .
L'(les) élément(s) constitutif(s) dudit matériau n'est (ne sont) pas per se original(aux) : au moins un borohydrure d'un métal alcalin ou alcalino-terreux, généralement un borohydrure d'un métal alcalin ou un borohydrure d'un métal alcalino-terreux ; les mélanges d'au moins deux borohydrures alcalins, d'au moins deux borohydrures alcalino-terreux, voire d'au moins un borohydrure alcalin et d'au moins un borohydrure alcalino-terreux (mélanges mixtes) n'étant toutefois nullement exclus. Ce qui est original, c'est la forme dudit matériau. De façon caractéristique, le(s)dit(s) élément(s) constitutif(s) a(ont) été conditionné(s) en une mousse solide présentant une surface spécifique telle qu'indiquée ci-dessus.The element (s) constituting (s) said material is (are) not per se original (aux): at least one borohydride of an alkali metal or alkaline earth metal, usually a borohydride of a alkali metal or borohydride of an alkaline earth metal; mixtures of at least two alkaline borohydrides, at least two alkaline earth borohydrides, or even at least one alkaline borohydride and at least one alkaline earth borohydride (mixed mixtures) are however not excluded. What is original is the shape of the material. Typically, the said constituent element (s) has been conditioned into a solid foam having a specific surface as indicated above.
Le matériau de l'invention est nouveau en ce qu'il s'agit d'une mousse solide présentant une telle surface spécifique. Cette notion de mousse solide est familière à l'homme du métier, dans des contextes différents de celui de l'invention. On entend par mousse solide dans lesdits contextes, et donc dans la présente description et les revendications annexées, un matériau solide homogène à fortes porosité et surface spécifique. Dans le cadre de la présente invention, la surface spécifique de ladite mousse est supérieure à 1,0 m2.g-1 (il s'agit d'une mousse) : elle est comprise entre 1,5 m2.g-1 et 10 m2.g-1. Il s'agit d'une porosité ouverte, libre, bien qu'il ne soit pas exclu que certains pores soient fermés.The material of the invention is new in that it is a solid foam having such a specific surface. This concept of solid foam is familiar to those skilled in the art, in contexts different from that of the invention. The expression "solid foam" in said contexts, and therefore in the present description and the appended claims, means a homogeneous solid material with a high porosity and a specific surface area. In the context of the present invention, the specific surface area of said foam is greater than 1.0 m 2 .g -1 (it is a foam): it is between 1.5 m 2 .g -1 and 10 m 2 .g -1 . It is an open porosity, free, although it is not excluded that some pores are closed.
La notion de surface spécifique, plus particulièrement employée pour caractériser un matériau, à l'état de poudre ou de mousse, est familière à l'homme du métier. Elle est classiquement déterminée par la méthode BET (voir plus loin).The concept of specific surface, more particularly used to characterize a material, in the form of powder or foam, is familiar to those skilled in the art. It is classically determined by the BET method (see below).
Les valeurs de surface spécifique énoncées ci-dessus pour les mousses de l'invention sont suffisamment élevées pour caractériser des mousses mais ne sont, en tout état de cause, pas très élevées (pour des mousses). Ainsi, les mousses de l'invention renferment-elles des pores suffisants gros (au vu desdites valeurs de surface spécifique) pour permettre une pénétration aisée du réactif d'hydrolyse au sein desdites mousses (la réaction d'hydrolyse se développe dans le volume desdites mousses), pour optimiser la réaction borohydrure(s)/réactif d'hydrolyse au sein desdites mousses. Les mousses de l'invention offrent en fait un optimum en termes de surface réactive (globale) et d'accessibilité à ladite surface réactive.The specific surface area values set forth above for the foams of the invention are sufficiently high to characterize foams but are, in any case, not very high (for foams). Thus, the foams of the invention contain sufficient large pores (in view of said specific surface values) for allow easy penetration of the hydrolysis reagent within said foams (the hydrolysis reaction is developed in the volume of said foams), to optimize the borohydride reaction (s) / hydrolysis reagent within said foams. The foams of the invention actually offer an optimum in terms of reactive surface (overall) and accessibility to said reactive surface.
Avantageusement, en référence au matériau constitutif de la mousse solide de l'invention, un seul alcalin ou alcalino-terreux est en cause et il est choisi dans le groupe comprenant le sodium (Na), le lithium (Li) et le magnésium (Mg). Le tétrahydroborate de sodium NaBH4 est le plus avantageux, car il est facile à produire et peu coûteux.Advantageously, with reference to the constituent material of the solid foam of the invention, only one alkali or alkaline earth metal is involved and it is chosen from the group comprising sodium (Na), lithium (Li) and magnesium (Mg). ). NaBH 4 sodium tetrahydroborate is the most advantageous because it is easy to produce and inexpensive.
Les poudres des borohydrures de base (matières premières utiles à l'obtention des mousses de l'invention : voir le procédé d'obtention décrit ci-après) présentent généralement une surface spécifique comprise entre 0,05 et 0,1 m2/g (l'homme du métier n'ignore pas que des valeurs aussi faibles dépendent du gaz absorbé pour la mise en oeuvre de la mesure). Les mousses de la présente invention ont une surface spécifique plus de 10 fois plus importante que celle desdites poudres des borohydrures de base (la mesure de surfaces spécifiques de cette ordre là est beaucoup moins dépendante de la nature du gaz absorbé). Il n'est toutefois pas exclu que des poudres de borohydrure, susceptibles d'être utilisées pour l'obtention de mousses de l'invention, présentent une surface spécifique plus élevée, et notamment une surface spécifique de l'ordre de celle indiquée pour les mousses de l'invention. La coïncidence de valeurs de surface spécifique (mousses/poudres) n'est que fortuite.The basic borohydride powders (raw materials useful for obtaining the foams of the invention: see the production process described below) generally have a specific surface area of between 0.05 and 0.1 m 2 / g. (The skilled person is aware that such low values depend on the gas absorbed for the implementation of the measure). The foams of the present invention have a surface area more than 10 times greater than that of said basic borohydride powders (the measurement of specific surfaces of this order is much less dependent on the nature of the gas absorbed). However, it is not excluded that borohydride powders, which can be used to obtain foams of the invention, have a higher specific surface, and in particular a specific surface area of the order of that indicated for the foams of the invention. The coincidence of specific surface values (foams / powders) is only fortuitous.
La mousse de borohydrure(s) de l'invention peut renfermer, en mélange intime avec (noyée dans) le(s)dit(s) borohydrure(s) (au sein de son(ses) élément(s) constitutif(s)), de la matière catalytique (des particules de matière catalytique) apte(s) à catalyser la réaction de génération d'hydrogène par hydrolyse du(des)dit(s) borohydrure(s). Cette matière catalytique, intervient évidemment en référence au débouché principal des mousses de l'invention, présenté dans l'introduction du présent texte. On note incidemment ici que les mousses de l'invention, catalysées ou non, peuvent avoir d'autres débouchés. Elles peuvent être utilisées dans d'autres contextes.The borohydride foam (s) of the invention may contain, in intimate mixture with (embedded in) the said borohydride (s) (within its constitutive element (s) ), catalytic material (particles of catalytic material) capable (s) to catalyze the reaction of hydrogen generation by hydrolysis of (or said) borohydride (s). This catalytic material, obviously intervenes with reference to the main outlet of the foams of the invention, presented in the introduction of this text. Incidentally, it is noted here that the foams of the invention, catalysed or not, may have other outlets. They can be used in other contexts.
La granulométrie de ladite matière catalytique est aussi faible que possible. Les particules de matière catalytique consistent donc généralement en des nanoparticules qui présentent un diamètre médian compris entre 1 et 100 nm, avantageusement compris entre 3 et 5 nm. De telles nanoparticules permettent d'obtenir un mélange intime avec le borohydrure métallique. Leur procédé d'obtention est par exemple décrit dans la référence suivante :
Les mousses catalysées de l'invention contiennent généralement de 0,5 % à 30 % en poids de matière catalytique, avantageusement au plus 10 %, très avantageusement entre 1 et 10 %.The catalysed foams of the invention generally contain from 0.5% to 30% by weight of catalytic material, advantageously at most 10%, very advantageously between 1 and 10%.
Ladite matière catalytique, en mélange intime avec le(s)dit(s) borohydrure(s), peut être constituée par au moins un métal choisi dans le groupe comprenant le platine (Pt), le ruthénium (Ru), le palladium (Pd), le cobalt (Co), le nickel (Ni), le fer (Fe), l'or (Au), l'argent (Ag), le manganèse (Mn), le rhénium (Re), le rhodium (Rh), le titane (Ti), le vanadium (V) et le cérium (Ce), ou par au moins un alliage, ou sel ou oxyde d'au moins un desdits métaux. Ces matières présentent l'avantage de catalyser efficacement les réactions d'hydrolyse des borohydrures.Said catalytic material, in intimate mixture with said borohydride (s), may consist of at least one metal selected from the group comprising platinum (Pt), ruthenium (Ru), palladium (Pd) ), cobalt (Co), nickel (Ni), iron (Fe), gold (Au), silver (Ag), manganese (Mn), rhenium (Re), rhodium (Rh) ), titanium (Ti), vanadium (V) and cerium (Ce), or by at least one alloy, or salt or oxide of at least one of said metals. These materials have the advantage of effectively catalyzing the hydrolysis reactions of borohydrides.
Avantageusement, le sel en cause est un chlorure, un borure ou un sel organométallique d'au moins un des métaux ci-dessus, et par exemple le borure de cobalt ou le borure de nickel, qui constituent tous deux de bons catalyseurs.Advantageously, the salt in question is a chloride, a boride or an organometallic salt of at least one of the above metals, and for example cobalt boride or nickel boride, both of which are good catalysts.
Les mousses de l'invention permettent de générer de l'hydrogène, en mettant en oeuvre une réaction hétérogène, solide - liquide, facilement contrôlable, quel que soit son degré d'avancement.The foams of the invention make it possible to generate hydrogen, by implementing a heterogeneous, solid-liquid, easily controllable reaction, whatever its degree of advancement.
Selon son deuxième objet, l'invention concerne un procédé de production de telles mousses.According to its second object, the invention relates to a method for producing such foams.
Ledit procédé comprend les étapes (de base) successives suivantes :
- la solubilisation, avec agitation, d'une poudre d'au moins un borohydrure de métal alcalin ou alcalino-terreux dans un solvant, solvant préférentiellement à bas point d'ébullition (en référence à la mise en oeuvre de son évaporation ultérieure), pour obtenir une solution,
- l'éventuel ajout de particules de matière catalytique non soluble dans ledit solvant, avantageusement de granulométrie nanométrique, pour l'obtention d'une suspension,
- le barbotage d'un gaz inerte (type Ar, N2) dans ladite solution ou suspension maintenue sous agitation,
- l'évaporation du solvant, sans arrêter ni l'agitation ni le barbotage, jusqu'à l'obtention d'un matériau pâteux, puis
- le chauffage sous pression réduite dudit matériau pâteux pour le sécher et obtenir une mousse solide dudit au moins un borohydrure.
- the solubilization, with stirring, of a powder of at least one alkali metal or alkaline earth metal borohydride in a solvent, preferably a low-boiling solvent (with reference to the implementation of its subsequent evaporation), for get a solution,
- the possible addition of non-soluble catalytic material particles in said solvent, advantageously of nanometric particle size, to obtain a suspension,
- sparging an inert gas (type Ar, N 2 ) in said solution or suspension kept under stirring,
- evaporation of the solvent, without stopping or stirring or bubbling, until a pasty material is obtained, and then
- heating under reduced pressure of said pasty material to dry and obtain a solid foam of said at least one borohydride.
On conçoit que les propriétés (porosité, surface spécifique) de la mousse solide obtenue dépendent des conditions de mise en oeuvre du procédé d'obtention de ladite mousse et plus particulièrement des conditions de mise en oeuvre de l'agitation, du barbotage et de l'évaporation du solvant. La gestion de ces conditions, leur optimisation, en vue du résultat recherché (valeurs de surface spécifique) relève des connaissances de l'homme du métier.It is conceivable that the properties (porosity, specific surface area) of the solid foam obtained depend on the conditions of implementation of the process for obtaining said foam and more particularly on the conditions for carrying out stirring, bubbling and blowing. Evaporation of the solvent. The management of these conditions, their optimization, in view of the desired result (specific surface values) falls within the knowledge of those skilled in the art.
En tout état de cause, il convient de souligner que l'agitation de la solution et le barbotage sont indispensables pour obtenir une mousse.In any case, it should be emphasized that agitation of the solution and bubbling are essential to obtain a foam.
Le "bloc" de mousse obtenu peut évidemment être concassé pour générer des morceaux (plus petits) de mousse.The "block" of foam obtained can obviously be crushed to generate pieces (smaller) of foam.
Pour obtenir une mousse de borohydrure(s) refermant de la matière catalytique, on met en oeuvre l'étape intermédiaire éventuelle précisée ci-dessus. Ainsi, le barbotage est-il mis en oeuvre dans une solution, en l'absence de matière catalytique, dans une suspension, en présence de matière catalytique.In order to obtain a borohydride foam (s) which closes with catalytic material, the optional intermediate step specified above is carried out. Thus, the bubbling is carried out in a solution, in the absence of catalytic material, in a suspension, in the presence of catalytic material.
L'homme du métier saura déterminer un solvant (solvant ou mélange de solvants) adapté à la mise en oeuvre du procédé ci-dessus, c'est-à-dire un solvant du(des) borohydrure(s) métallique(s) retenu(s), solvant dans lequel la matière catalytique qui intervient éventuellement est insoluble. On mentionne, par exemple, le solvant ammoniac liquide pour les couples borohydrure de sodium et chlorure ou borure métallique.Those skilled in the art will be able to determine a solvent (solvent or solvent mixture) suitable for carrying out the above process, that is to say a solvent for the metal borohydride (s) retained. (s) solvent in which the catalytic material which intervenes possibly is insoluble. For example, mention is made of the liquid ammonia solvent for the sodium borohydride and metal chloride or boride pairs.
On comprend que le procédé de l'invention présente l'avantage d'être indépendant de la granulométrie du borohydrure (matière première), ledit borohydrure étant dissous dans la solution.It is understood that the method of the invention has the advantage of being independent of the particle size of the borohydride (raw material), said borohydride being dissolved in the solution.
Pour ce qui concerne la granulométrie de la matière catalytique, elle revêt une importance certaine et dans le cadre du procédé de l'invention elle peut être optimisée sans difficultés. Elle est en effet parfaitement maîtrisable dans la mesure où ladite matière catalytique intervient à l'état solide (à l'état de particules) et reste en suspension (dans le même état solide, à l'état de particules).Regarding the particle size of the catalytic material, it has a certain importance and in the context of the process of the invention it can be optimized without difficulty. It is indeed perfectly controllable insofar as said catalytic material intervenes in the solid state (in the form of particles) and remains in suspension (in the same solid state, in the form of particles).
On rappelle ici que les particules de matière catalytique présentent généralement un diamètre médian compris entre 1 et 100 nm, avantageusement compris entre 3 et 5 nm. De telles nanoparticules permettent d'obtenir un mélange intime avec le borohydrure métallique.It is recalled here that the particles of catalytic material generally have a median diameter of between 1 and 100 nm, advantageously between 3 and 5 nm. Such nanoparticles make it possible to obtain an intimate mixture with the metal borohydride.
La présente invention concerne également un procédé de génération d'hydrogène par hydrolyse d'au moins une mousse de l'invention (mousse telle que décrite ci-dessus et/ou telle que produite par le procédé décrit ci-dessus). Ledit procédé est avantageusement mis en oeuvre pour l'alimentation (en hydrogène) d'une pile à combustible. Lorsque la mousse renferme de la matière catalytique, l'activation de la réaction d'hydrolyse ne nécessite aucun transport de catalyseur par la phase hydrolysante.The present invention also relates to a process for generating hydrogen by hydrolysis of at least one foam of the invention (foam as described above and / or as produced by the method described above). Said method is advantageously used for the supply (in hydrogen) of a fuel cell. When the foam contains catalytic material, activation of the hydrolysis reaction requires no catalyst transport by the hydrolyzing phase.
L'invention est ci-après illustrée par la description d'un mode de mise en oeuvre particulier du procédé (exemple) ainsi que par les figures annexées. L'objet de l'invention ne se limite cependant pas à ce mode de mise en oeuvre particulier et d'autres modes de mise en oeuvre du procédé sont évidemment possibles.The invention is hereinafter illustrated by the description of a particular mode of implementation of the method (example) as well as by the appended figures. The object of the invention is not however limited to this particular mode of implementation and other modes of implementation of the method are obviously possible.
Les
Les
Lesdites figures sont commentées dans l'exemple qui suit.Said figures are commented on in the following example.
On présente, ci-dessous, un exemple pratique de mise en oeuvre du procédé - objet de l'invention - permettant de fabriquer une mousse - objet de l'invention - présentement une mousse de borohydrure de sodium renfermant une matière catalytique (borure de cobalt).Below is a practical example of implementation of the method - object of the invention - for manufacturing a foam - object of the invention - presently a sodium borohydride foam containing a catalytic material (cobalt boride ).
Dans ce mode de réalisation particulier, conforme au procédé objet de l'invention, le borohydrure de sodium, de formule NaBH4 est dit sec, car il est préalablement déshydraté à 150°C sous vide primaire pendant 2 heures.In this particular embodiment, in accordance with the process which is the subject of the invention, the sodium borohydride, of formula NaBH 4, is said to be dry because it is previously dehydrated at 150 ° C. under primary vacuum during 2 hours.
On rappelle que, dans le cadre du procédé de l'invention, la granulométrie ou surface spécifique du borohydrure (de départ) n'a pas d'importance puisque ledit borohydrure à vocation à être dissous. A titre de comparaison avec la mousse objet de l'invention obtenue en fin de procédé (voir les
Le procédé exemplifié comprend également la production des particules de matière catalytique, par réduction d'un sel ou d'un alliage ou d'un oxyde d'au moins un métal, selon des méthodes décrites dans la littérature.The exemplified process also comprises the production of the particles of catalytic material, by reduction of a salt or an alloy or an oxide of at least one metal, according to methods described in the literature.
La granulométrie des particules de matière catalytique (borure de cobalt, dans le présent exemple) est importante dans le cadre du procédé de l'invention, puisque ces particules restent en suspension dans le solvant (dans la suite du procédé) jusqu'à évaporation dudit solvant. On choisit avantageusement les plus petites granulométries possibles, i.e. des particules d'un diamètre médian préférentiellement inférieur à 100 nm, très préférentiellement inférieur à 10 nm (voir ci-dessus).The particle size of the particles of catalytic material (cobalt boride, in the present example) is important in the context of the process of the invention, since these particles remain in suspension in the solvent (in the following process) until evaporation of said solvent. The smallest possible particle sizes are advantageously chosen, i.e. particles having a median diameter preferably less than 100 nm, very preferably less than 10 nm (see above).
Dans une préparation typique, 100 ml d'ammoniac gazeux sont condensés dans un réacteur refroidi à -35°C et surmonté d'un piége à carboglace. Après liquéfaction de l'ammoniac, 5 g de borohydrure de sodium sec (0,132 mmol) sont introduits rapidement sous vigoureuse agitation (au moyen d'une turbine de Rushton à 6 pales, équipement bien connu de l'homme du métier), conduisant à la solubilisation totale du borohydrure. Une masse de borure de cobalt (de faible granulométrie) est ajoutée, correspondant à un taux de 10% de la masse de borohydrure introduite. Après l'introduction du catalyseur, un barbotage d'argon (débit de 20 l/min) est mis en oeuvre au moyen d'un tube capillaire plongeur dans la solution et la température est ramenée doucement jusqu'à l'ambiante (1°C/3min), ce qui entraîne l'évaporation de l'ammoniac. L'agitation est maintenue pendant toute la durée (environ 20 minutes) de l'évaporation de l'ammoniac. Lorsque le mélange devient pâteux dans le réacteur, le bullage d'argon et l'agitation sont arrêtés. Le milieu est alors mis sous pression réduite jusqu'à une pression de 10-2 mbar et chauffé 8h à 60°C jusqu'à l'obtention d'un solide gris correspondant à la mousse de borohydrure formée renfermant la matière catalytique (mousse qui constitue un exemple de mousse conforme à la présente invention). Cette mousse se doit d'être stockée à l'abri de l'humidité.In a typical preparation, 100 ml of ammonia gas is condensed in a reactor cooled to -35 ° C and topped with a dry ice trap. After liquefaction of the ammonia, 5 g of dry sodium borohydride (0.132 mmol) are rapidly introduced under vigorous stirring (by means of a 6-blade Rushton turbine, equipment well known to those skilled in the art), leading to the total solubilization of the borohydride. A mass of cobalt boride (small particle size) is added, corresponding to a level of 10% of the mass of borohydride introduced. After the introduction of the catalyst, an argon bubbling (flow rate of 20 l / min) is implemented by means of a capillary tube plunger in the solution and the temperature is gently brought down to ambient (1 ° C / 3min), which causes the evaporation of ammonia. Stirring is maintained throughout the duration (about 20 minutes) of evaporation of ammonia. When the mixture becomes pasty in the reactor, bubbling argon and stirring are stopped. The medium is then put under reduced pressure to a pressure of 10 -2 mbar and heated for 8 hours at 60 ° C. until a gray solid corresponding to the formed borohydride foam containing the catalytic material (foam which is an example of a foam according to the present invention). This foam must be stored away from moisture.
Sa couleur grise témoigne de la présence des particules de la matière catalytique, en l'occurrence du borure de cobalt. L'analyse élémentaire confirme effectivement la présence de 10 % pondéral de borure de cobalt, en mélange intime avec (noyé dans) le borohydrure de sodium. Ladite analyse élémentaire ("ICP : Induction Couple Plasma") donne la composition pondérale ci-après : 54,7% de Na, 27% de B, 7,3% de Co et 11% de H2.Its gray color testifies to the presence of the particles of the catalytic material, in this case cobalt boride. The elemental analysis indeed confirms the presence of 10% by weight of cobalt boride, in intimate mixture with (embedded in) sodium borohydride. Said elemental analysis ("ICP: Couple Plasma Induction") gives the following weight composition: 54.7% Na, 27% B, 7.3% Co and 11% H 2 .
De plus, conformément à la caractéristique principale de l'invention, le matériau obtenu se présente sous la forme d'une mousse à pores ouverts, comme le montrent les trois images obtenues par microscopie électronique à balayage, pour différents grossissements, montrées sur les
Il a été montré que la cinétique de production d'hydrogène (exprimée en µl de H2/s) de la réaction d'hydrolyse mise en oeuvre sur la mousse du présent exemple est au moins 3,5 fois plus rapide que celle relevée par hydrolyse mise en oeuvre sur un simple mélange broyé des ingrédients de l'exemple.It has been shown that the hydrogen production kinetics (expressed in μl of H 2 / s) of the hydrolysis reaction carried out on the foam of the present example is at least 3.5 times faster than that recorded by hydrolysis implemented on a simple ground mixture of the ingredients of the example.
Le matériau conforme à la présente invention permet de limiter la formation d'une couche passivante, c'est-à-dire d'une couche constituée des sous-produits de la réaction d'hydrolyse. En effet, les métaborates se formant par contact entre l'eau, le catalyseur et le tétrahydroborate de sodium se trouvent répartis à la surface de la mousse, et ainsi, ne constituent pas une couche continue et bloquante.The material according to the present invention makes it possible to limit the formation of a passivating layer, that is to say a layer consisting of the by-products of the hydrolysis reaction. Indeed, the metaborates formed by contact between water, the catalyst and sodium tetrahydroborate are distributed on the surface of the foam, and thus, do not constitute a continuous and blocking layer.
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FR0758471A FR2922542B1 (en) | 2007-10-22 | 2007-10-22 | BOROHYDRIDE FOAM (S); PROCESS FOR PRODUCING; GENERATION OF HYDROGEN AND FUEL CELLS USING THE SAME |
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WO2005005311A2 (en) | 2003-05-14 | 2005-01-20 | Lynntech, Inc. | Hydrogen generator |
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FR2892111A1 (en) | 2005-10-19 | 2007-04-20 | Commissariat Energie Atomique | Material for generating hydrogen gas by hydrolyzing tetrahydroborate powder of alkaline/alkaline-earth metals |
-
2007
- 2007-10-22 FR FR0758471A patent/FR2922542B1/en not_active Expired - Fee Related
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2008
- 2008-10-21 EP EP08167150A patent/EP2053018A1/en not_active Withdrawn
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US20070020172A1 (en) | 2005-02-08 | 2007-01-25 | Hyenergy Systems, Inc. | Solid chemical hydride dispenser for generating hydrogen gas |
FR2892111A1 (en) | 2005-10-19 | 2007-04-20 | Commissariat Energie Atomique | Material for generating hydrogen gas by hydrolyzing tetrahydroborate powder of alkaline/alkaline-earth metals |
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H.I. SCHLESINGER, H. BROWN, A.E. FINHOLT, J.G.GILBREATH, H.R. HOEKSTRA, E.K. HYDE: "Sodium Borohydride, Its Hydrolysis and its Use as a Reducing Agent and in the Generation of Hydrogen", JOURNAL OF AMERICAN CHEMICAL SOCIETY, vol. 75, 1953, pages 215 - 219, XP002486386 * |
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FR2922542B1 (en) | 2010-01-01 |
FR2922542A1 (en) | 2009-04-24 |
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